This invention relates to atomic beam deflection techniques and to advanced coherent optical techniques for isotope separation.
Recently, a new radiation pressure technique for deflecting atomic or molecular beams or for separating isotopes was proposed by I. Nebenzahl et al, Applied Physics Letters, Vol. 25, page 327 (September 1974). Their scheme is inherently efficient as compared to radiation pressure techniques that use isotropic reradiation of absorbed energy, because their technique returns the reradiated energy as a coherent optical beam which may be re-used and actually increases the force that can be exerted on the atoms. The coherent reradiation is achieved by a chirped optical pulse which forms the "pushing" beam and produces an "adiabatic rapid passage" effect on the atoms, molecules or isotopes being pushed. The chirped pulse causes all of the atoms in the atomic beam with the correct transition frequency to go to the excited state, with each atom absorbing one photon. The pulse is reflected back through the atomic beam at the appropriate time interval, causing the atoms to return in a coherent fashion to the ground state by each emitting a photon. The double pass of the light through the atomic beam appears to be essentially a specular reflection of one photon from each atom. Hence, twice the momentum of the photon is transferred to the atom; and the atom's trajectory is deflected. The slight red shift of the light is insignificant to its re-use in such a chirped scheme.
We have recognized that it would be desirable to retain the inherent efficiency of the Nebenzahl et al proposal while avoiding the need for a baseband frequency-modulating field to achieve the necessary chirp and avoiding the need for amplifying frequency-modulated light pulses.